DAViCal

ownCloud Core is a self-hosted file sharing and collaboration platform for storing, syncing, and sharing files, calendars, contacts, and other data.

Nextcloud Server is a self-hosted platform for storing, syncing, sharing, and collaborating on files, contacts, calendars, and other data.

NextcloudPi is a ready-to-use build and deployment image for running Nextcloud on supported hardware, containers, and Debian-based systems.

SOGo is a free and open source groupware solution.

Baïkal is a CalDAV and CardDAV server for syncing calendars and contacts.

bewCloud is a self-hosted web app for managing cloud-like personal data, with support for calendar, contacts, file sharing, and related sync features.

GroupOffice is an open-source groupware and CRM platform for enterprises and the public sector.

EGroupware is a web-based groupware platform for collaboration and business productivity.

A fully translatable DAV server with a web admin dashboard and frontend for calendars, contacts, and file access.

SnappyMail is a lightweight, modern web-based email client forked from RainLoop.

tine is a groupware and collaboration platform for companies and organizations, combining core productivity features with add-ons and enterprise deployment options.

Groupware including email, calendar/scheduling, address books, forums, mailing lists, IM, wiki and blog engines, RSS aggregation and more.